Spanish police said on Saturday they had broken up a criminal gang that used helicopters to smuggle hashish from Morocco, in a rare operation against aerial drug trafficking, According to Reuters,

The helicopters, which could carry between 500 and 900 kilograms (1,100-2,000 pounds) of drugs, flew across the Mediterranean to southern Spain, where the hashish was then transported by road to other parts of Europe, Civil Guard spokesperson Gonzalo Lopez said.

Police seized one helicopter in an isolated warehouse, along with 657 kg of hashish, five firearms, cash and vehicles during raids in the provinces of Malaga, Almeria and Murcia.

Six people were arrested in the operation, which also involved Moroccan, Belgian and Swedish law enforcement agencies.

“It is rare for helicopters to be used to smuggle drugs but occasionally they (criminal gangs) do try. Remember that helicopters are easy to detect and hard to buy on the black market,” a police source told Reuters.

Earlier this year, Spanish police dismantled crime groups that used drones to transport drugs from Morocco to Spain.

Spain’s geographic position makes it a key entry point for hashish into Europe, mainly from Morocco, and cocaine smuggled from Latin America. Hashish is usually smuggled by sea, sometimes using high-speed launches or jet-skis.

The six suspects have been remanded in custody on suspicion of drug trafficking, belonging to a criminal organisation and possession of firearms.

The Civil Guard did not say when the operation, called Giro, took place.